Adverse environmental conditions can render a location and/or building unsatisfactory for living or working. One type of adverse environmental conditions is air contaminants such as vapor intrusion or radon gas intrusion, which can occur when volatile chemicals contained in contaminated soil or groundwater emit vapors or other air contaminants Such vapors and/or air contaminants can seep through the subsurface of a nearby or overlying building, entering the living or working space therein. The vapors and/or air contaminants emitted from the volatile chemicals can be harmful to the occupants of such buildings. Vapor intrusion may occur, for example, when land is repurposed from an original use, involving the use of such volatile chemicals (e.g., a gas station or chemical production plant), to another use (e.g., a business or residential building).
Federal and local regulations may require the rehabilitation of any location in which vapor intrusion has been detected to ensure a safe workplace or living space. Oftentimes, mitigation of vapor intrusion includes periodic, on-site sampling of the air quality of the workplace/living space. In some cases, the mitigation procedures may include remediation of the contamination source within the land itself. Alternatively, active mitigation systems may be used to mitigate the vapor intrusion. In many active mitigation systems, the contaminated area (e.g., the sub-slab ground) is depressurized relative to the living/working space. For example, a typical mitigation procedure may include the use of air conduits, which are sunk into the ground (e.g., through the subsurface of the building) and exhaust to the outside open air to lower the pressure of the contaminated area and facilitate propagation of any harmful vapors away from the workplace/living space. Such mitigation systems may include fans to depressurize the contaminated area and further facilitate the safe propagation of the harmful vapors. If so, proper fan operation may also be periodically checked as part of the periodic, on-site review.